Whole Foods CEO John Mackey used to think Amazon wouldn't thrive in the grocery delivery business, according to a 2015 interview with Bloomberg Businessweek, starkly contrasting the recent deal he stuck with the company.

Mackey reportedly predicted the e-commerce giant's move into grocery delivery through its AmazonFresh initiative, a capitalize-intensive service, would be "Amazon's Waterloo" moment.

Amazon said Friday it plans to acquire Whole Foods Market in a deal valued at $13.7 billion. Shares of Whole Foods soared 30 percent after the announcement, and Amazon stock rose 3 percent.